Objectives: Immediate postpartum placement of the LNG-IUS can decrease unplanned pregnancy in the US. The objective of this study was to compare breastfeeding prevalence between women who receive the LNG-IUS immediately postpartum, or 4-6 weeks later. Methods: We conducted a parallel, randomized trial with 1:1 allocation at Women’s Hospital of North Carolina. The LNG-IUS was inserted after an uncomplicated vaginal delivery prior to hospital discharge, or at the first postpartum visit. All women stated intent to breastfeed their infants. The primary outcome was self-report of any breastfeeding at 6 months. A Data Safety Monitoring Boar established a priori stopping rules. Participants, research staff, and data analyzers were not blinded to allocation. Results: 147 women were screened, 61 women enrolled antepartum, and 35 women were randomized postpartum. The study was stopped early because the expulsion rate met a priori stopping rules. Seventeen women were allocated to immediate insertion and 18 to postpartum insertion. Primary analysis was intent to treat. Seven (41%) women in the immediate arm and 13 women (72%) in the control arm had the original LNG-IUS in situ at the 6-month study visit. The proportion of women reporting any breastfeeding at 6-months was similar in the immediate compared to the postpartum group (59% and 50%; RR and 95% confidence interval 1.26 (0.71, 2.23). Conclusions: Immediate postpartum LNG-IUS should be reserved for women who state extreme difficulty in returning for a postpartum clinic visit. Breastfeeding women or women in research studies are not good candidates for immediate postpartum LNG-IUS insertion.